Measurement apparatus

Abstract

A method for determining biological indicators, the method including, in a processing system causing at least one radiation attenuation measurement to be performed and determining at least one first biological indicator using determined radiation attenuation. In addition to this, method includes causing at least one impedance measurement to be performed and determining at least one second biological indicator using a determined impedance measurement.

The claims defining the invention are as follows: 
     
       1. A method for use in determining a presence, absence or degree of lymphoedema using a processing system, comprising the steps of:
 a) performing at least one radiation attenuation measurement; wherein the processing system uses a signal generator to control a radiation source for performing the radiation attenuation measurement; 
 b) determining limb volumes for a subject using a determined radiation attenuation; wherein a detector measures an intensity of transmitted radiation and returns the intensity of transmitted radiation to the processing system for determination of limb volumes for the subject; 
 c) performing at least one impedance measurement; wherein the processing system uses a controller to control a signal generator and sensor for performing the at least one impedance measurement; 
 d) determining fluid levels in the subject using a determined impedance measurement wherein the controller returns the at least one impedance measurement to the processing system, or wherein the controller returns at least one derived impedance parameter value to the processing system for determining fluid levels in the subject; and, 
 e) using the processing system to determine an indication of the presence, absence or degree of lymphoedema by:
 i) using the limb volumes to detect the presence or absence of lymphoedema; 
 ii) using the fluid levels to detect the presence, absence or degree of lymphoedema; and, 
 iii) detecting that lymphoedema is at an early stage if lymphoedema is detected using the fluid levels but not using the limb volumes. 
 
 
     
     
       2. The method according to  claim 1 , further comprising: performing the radiation attenuation measurement by:
 a) exposing the subject to radiation from the radiation source; and, 
 b) determining the attenuation of radiation transmitted through the subject. 
 
     
     
       3. The method according to  claim 2 , further comprising:
 a) causing the radiation source to scan along a length of the subject; and, 
 b) receiving an indication of radiation attenuation from a detector. 
 
     
     
       4. The method according to  claim 1 , further comprising: performing the impedance measurement by:
 a) applying one or more electrical signals to the subject using a first set of electrodes; 
 b) determining an indication of electrical signals measured across a second set of electrodes applied to the subject; and, 
 c) determining from the indication and the one or more applied signals, the fluid levels. 
 
     
     
       5. The method according to  claim 1 , further comprising:
 a) determining at least one measurement procedure to be performed; and, 
 b) performing the radiation attenuation and impedance measurements in accordance with the determined measurement procedure. 
 
     
     
       6. The method according to  claim 5 , further comprising:
 a) selecting instructions corresponding to the measurement procedure; and 
 b) transferring the instructions to a second processing system, the second processing system being for:
 i) generating, using the instructions, control signals, the control signals being used to apply one or more signals to the subject; 
 ii) receiving an indication of the one or more signals applied to the subject; 
 iii) receiving an indication of one or more signals measured across the subject; and 
 iv) performing, using the instructions, at least preliminary processing of the indications to thereby allow impedance values to be determined. 
 
 
     
     
       7. The method according to  claim 5 , further comprising:
 a) determining at least one electrode arrangement associated with the determined measurement procedure; 
 b) displaying a representation indicative of the electrode arrangement; and, 
 c) performing the impedance measurement once the electrodes have been arranged in accordance with the displayed representation. 
 
     
     
       8. The method according to  claim 1 , wherein fluid levels are indicative of at least one of:
 a) an index based on the ratio of extra- to intra-cellular fluid; 
 b) an index based on an impedance parameter value; 
 c) an intracellular fluid volume; and, 
 d) an extracellular fluid volume. 
 
     
     
       9. The method according to  claim 1 , further comprising:
 a) comparing the fluid levels to at least one of:
 i) a predetermined reference; 
 ii) fluid levels determined for at least one other body segment; 
 iii) previously determined fluid levels; and, 
 
 b) determining an indication of the presence, absence or degree of oedema using the results of the comparison. 
 
     
     
       10. The method according to  claim 9 , wherein the reference comprises at least one of:
 a) a predetermined threshold; 
 b) a tolerance determined from a normal population; 
 c) a predetermined range; and, 
 d) fluid levels previously determined for the subject. 
 
     
     
       11. The method according to  claim 1 , further comprising:
 a) determining a first measured impedance indicative of a measured impedance for a first half of a first limb; 
 b) determining a second measured impedance indicative of a measured impedance for a second half of the first limb; 
 c) determining a third measured impedance indicative of a measured impedance for the first limb; 
 d) determining a derived impedance indicative of an impedance for the first half of the first limb using the second and third measured impedances; and, 
 e) comparing the first measured impedance and the derived impedance. 
 
     
     
       12. The method according to  claim 11 , further comprising:
 a) determining if any electrodes are incorrectly positioned in accordance with the results of the comparison of the first measured impedance and the derived impedance; and, 
 b) generating an indication of any incorrectly positioned electrodes. 
 
     
     
       13. The method according to  claim 1 , further comprising:
 a) determining a measured impedance value for at least one body segment; 
 b) for each body segment, and using the measured impedance values, determining at least one impedance parameter value; and, 
 c) using each determined impedance value to determine the fluid levels. 
 
     
     
       14. The method according to  claim 13 , further comprising:
 a) determining at least one impedance parameter value using each determined impedance value; and, 
 b) determining the fluid levels using the at least one impedance parameter value. 
 
     
     
       15. The method according to  claim 13 , further comprising:
 a) determining a plurality of measured impedance values for each body segment, each measured impedance value being measured at a corresponding measurement frequency; and, 
 b) determining impedance parameter values based on the plurality of measured impedance values. 
 
     
     
       16. The method according to  claim 13 , wherein the parameter values include R 0  and R ∞ , wherein:
 a) R 0  is the resistance at zero frequency; and, 
 b) R ∞  is the resistance at infinite frequency. 
 
     
     
       17. The method according to  claim 16 , further comprising:
 a) monitoring changes over time for at least one of:
 i) R 0 ; 
 ii) R ∞ ; and 
 iii) a difference between R 0  and R ∞ ; and 
 
 b) a vector indication of an impedance measurement. 
 
     
     
       18. The method according to  claim 16 , further comprising:
 a) determining values for parameters R 0  and R ∞  from the measured impedance values; and, 
 b) determining the indicator by calculating the index (I) using the equation: 
 
       
         
           
             
               I 
               = 
               
                 
                   
                     R 
                     ∞ 
                   
                   
                     
                       R 
                       0 
                     
                     - 
                     
                       R 
                       ∞ 
                     
                   
                 
                 . 
               
             
           
         
       
     
     
       19. The method according to  claim 16 , further comprising: determining the parameter values using the equation: 
       
         
           
             
               Z 
               = 
               
                 
                   R 
                   ∞ 
                 
                 + 
                 
                   
                     
                       R 
                       0 
                     
                     - 
                     
                       R 
                       ∞ 
                     
                   
                   
                     1 
                     + 
                     
                       
                         ( 
                         
                           j 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           ωτ 
                         
                         ) 
                       
                       
                         ( 
                         
                           1 
                           - 
                           α 
                         
                         ) 
                       
                     
                   
                 
               
             
           
         
       
       where:
 Z is the measured impedance at angular frequency ω, 
 τ is a time constant, and 
 α has a value between 0 and 1. 
 
     
     
       20. The method according to  claim 1 , further comprising: determining the fluid levels as an extracellular fluid volume using the equation: 
       
         
           
             
               
                 ECV 
                 Segment 
               
               = 
               
                 
                   C 
                   Segment 
                 
                 ⁢ 
                 
                   
                     ρ 
                     Segment 
                   
                   ⁡ 
                   
                     ( 
                     
                       
                         L 
                         Segment 
                         2 
                       
                       
                         R 
                         Segment 
                       
                     
                     ) 
                   
                 
               
             
           
         
         Where ECV=Extracellular fluid volume
 C Segment =Geometry constant which is 1 for an arm or leg and 4 for the thoracic cavity 
 L Segment =Length of the segment in cm 
 R Segment =Resistance of the segment in Ohm 
 ρ Segment =Resistivity coefficient which is nominally 47 Ohm/cm. 
 
       
     
     
       21. The method according to  claim 20 , further comprising: determining the extracellular fluid volume for the entire body using the equation:
   ECV Total =2(ECV arm +ECV leg )+ECV trunk.    
 
     
     
       22. The method according to  claim 1 , further comprising: performing the at least one impedance measurement by:
 a) applying a first signal to the subject; 
 b) determining an indication of a second signal measured across the subject; 
 c) determining an imbalance using the indication of the second signal; 
 d) determining a modified first signal in accordance with the imbalance; and, 
 e) applying the modified first signal to the subject to thereby allow at least one impedance measurement to be performed. 
 
     
     
       23. The method according to  claim 22 , further comprising: determining the modified first signal so as to minimize the imbalance. 
     
     
       24. The method according to  claim 1 , wherein the method is performed using an apparatus comprising:
 a) at least two electrode systems, each electrode system comprising:
 i) a signal generator for applying a first signal to be applied to the subject; 
 ii) a sensor for sensing a second signal across the subject; 
 iii) a first electrode for coupling the signal generator to the subject; and, 
 iv) a second electrode for coupling the sensor to the subject; and, 
 
 b) a measuring device for controlling the electrode systems to allow impedance measurements to be performed; and, 
 c) at least two leads for connecting the measuring device to the electrode systems, and wherein the leads are arranged to at least one of:
 i) extend from the measuring device in different directions to thereby reduce inductive coupling therebetween; and, 
 ii) minimize the lead length. 
 
 
     
     
       25. Apparatus for use in determining a presence, absence or degree of lymphoedema, comprising a processing system for:
 a) performing at least one radiation attenuation measurement; wherein the processing system is coupled to a signal generator to control a radiation source for performing the radiation attenuation measurement; 
 b) determining limb volumes for a subject using a determined radiation attenuation; wherein the processing system is coupled to a detector and wherein the detector determines a transmitted radiation measurement and returns the transmitted radiation measurement to the processing system for determination of limb volumes for the subject; 
 c) performing at least one impedance measurement wherein the processing system is coupled to a controller to control a signal generator and sensor for performing the at least one impedance measurement; 
 d) determining fluid levels in the subject using a determined impedance measurement; wherein the controller returns the at least one impedance measurement to the processing system, or wherein the controller returns at least one derived impedance parameter value to the processing system for determining fluid levels in the subject; and 
 e) determining an indication of the presence, absence or degree of lymphoedema by the processing system by:
 i) using the limb volumes to detect the presence or absence of lymphoedema; 
 ii) using the fluid levels to detect the presence, absence or degree of lymphoedema; and, 
 
 f) detecting that lymphoedema is at an early stage if lymphoedema is detected by the processing system using the fluid levels but not using the limb volumes. 
 
     
     
       26. The apparatus according to  claim 25 , further comprising: a drive system that moves the radiation source and detector relative to the subject, to thereby expose the subject to the radiation. 
     
     
       27. The apparatus according to  claim 25 , further comprising:
 a) a support surface for supporting the subject; and, 
 b) one or more leads at least partially embedded within the support surface, the leads being for use in performing the impedance measurement procedure. 
 
     
     
       28. The apparatus according to  claim 25 , further comprising:
 a) an arm for supporting a detector; and, 
 b) one or more leads at least partially embedded within the arm, the leads being for performing the impedance measurement procedure. 
 
     
     
       29. The apparatus according to  claim 27 , wherein the leads are radiolucent. 
     
     
       30. The apparatus according to  claim 25 , further comprising: electrodes provided as part of at least one of:
 a) a foot plate; 
 b) a hand plate; 
 c) a band electrode; and, 
 d) a cuff. 
 
     
     
       31. The apparatus according to  claim 25 , wherein:
 the signal generator is configured to apply one or more electrical signals to the subject using a first set of electrodes; and further comprising: 
 a sensor for measuring electrical signals measured across a second set of electrodes; and wherein, 
 a) the controller is configured for:
 i) controlling the signal generator; and, 
 ii) determining the indication of the measured electrical signals. 
 
 
     
     
       32. The apparatus according to  claim 31 , wherein the controller performs the steps of:
 a) receiving instructions from the processing system; 
 b) generating, using the instructions, control signals, the control signals being used to apply one or more signals to the subject; 
 c) receiving an indication of the one or more signals applied to the subject; 
 d) receiving an indication of one or more signals measured across the subject; and 
 e) performing, using the instructions, at least preliminary processing of the indications to thereby allow impedance values to be determined. 
 
     
     
       33. The apparatus according to  claim 25 , wherein the processing system performs the impedance measurements by:
 a) applying a first signal to the subject; 
 b) determining an indication of a second signal measured across the subject; 
 c) determining an imbalance using the indication of the second signal; 
 d) determining a modified first signal in accordance with the imbalance; and 
 e) applying the modified first signal to the subject to thereby allow at least one impedance measurement to be performed. 
 
     
     
       34. The apparatus according to  claim 25 , further comprising: leads for connecting a measuring device to an electrode system, the electrode system comprising a signal generator and a sensor, and the leads comprising:
 a) at least two connections for connecting the measuring device and the signal generator, and the measuring device and the sensor; and, 
 b) a shield for each of the at least two connections, the shields being electrically connected, and connected to a reference potential in each of the measuring device and the electrode system. 
 
     
     
       35. The apparatus according to  claim 25 , further comprising:
 a) at least two electrode systems, each electrode system comprising:
 i) a signal generator for applying a first signal to be applied to the subject; 
 ii) a sensor for sensing a second signal across the subject; 
 iii) a first electrode for coupling the signal generator to the subject; and, 
 iv) a second electrode for coupling the sensor to the subject; and, 
 
 b) a measuring device for controlling the electrode systems to allow impedance measurements to be performed; and, 
 c) at least two leads for connecting the measuring device to the electrode systems, the leads being arranged to at least one of:
 i) extend from the measuring device in different directions to thereby reduce inductive coupling therebetween; and, 
 ii) minimize the lead length.